Receptor Tyrosine Kinase (RTK) inhibitors have revolutionized the treatment of several cancer types, but the eventual emergence of acquired resistance remains a major limitation of clinical benefit. Recent studies by our group and others have shown that acquired resistance is often characterized by extensive tumor heterogeneity, with multiple resistance mechanisms emerging simultaneously in distinct tumor subclones within an individual patient. This heterogeneity presents a formidable therapeutic obstacle, as therapies designed to overcome one specific resistance mechanism may be unable to suppress subclones harboring other resistance mechanisms, leading to clonal outgrowth and treatment failure. To develop and model strategies to overcome heterogeneous resistance to RTK inhibitors, we will perform a comprehensive assessment of acquired resistance to MET inhibition. MET is a critical RTK that is of growing therapeutic importance, with dramatic responses observed with MET inhibitors in the ~4% of gastroesophageal cancers (GEC) with MET amplification and ~5% of non-small cell lung cancer (NSCLC) patients with MET exon 14 skipping. We will employ a systematic liquid biopsy platform for circulating tumor DNA analysis, coupled with serial tumor biopsies, and a rapid autopsy program, to define the molecular landscape and heterogeneity of acquired resistance to MET inhibition. Through detailed mechanistic studies, we will attempt to identify common signaling nodes upon which multiple resistance mechanisms converge, which may represent ?universal? targets to intercept multiple heterogeneous resistance mechanisms simultaneously. We will also evaluate the potential for sequential inhibition strategies coupled with real-time ctDNA monitoring to overcome multiple resistance mechanisms that do not share a common signaling output. These approaches have the potential to create a new standard for surmounting tumor heterogeneity in the setting of acquired resistance, and we anticipate that principles defined by these studies will be broadly applicable to other RTK inhibitor paradigms.